Grinding machine



Juli@ 4, 1968 G. H. LocKwooD ETAL 3,385,210

GRINDING MACHINE Filed April 2l, 1965 ,38 la Hl 3/ mvEN'roRs (jeorqe fl. ocKu/ooci BY `freal Thomas 'H o may United States Patent() 3,386,210 GRINDING MACHiNE George H. Lockwood, Fort Lauderdaic, Fla., and Fred Thomas, Worcester, Mass., assignors to The Heald Machine Company, Worcester, Mass., a corporation of Delaware Filed Apr. 21, 1955, Ser. No. 449,817 Ciaims. (Cl. 51-5) ABSTRACT 0F THE DISCLGSURE The invention relates to a grinding machine and, more particularly, to such an apparatus in which the abrasive wheel is passed over a diamond for a dressing operation, but on a return pass metailic deformation is used to prevent contact between the wheel and the diamond.

In the operation of grinding machines, it is common practice to withdraw the abrasive wheel from the surface of the workpiece before the grinding operation is finished and to dress the wheel before returning the wheel to the workpiece for the completion of the operation. In this way, the wheel is guaranteed a smooth geometrically correct surface during the final portion o-f the grinding operation. In the case of an internal grinding machine, for instance, the wheel is withdrawn axially from the bore and, as it passes out of the bore, it is moved lengthwise past a fixed diamond. This diamond removes a layer of abrasive from the surface of the wheel, trues the wheel, and produces a smooth surface on it. ln a dressing operation, however, a good dressing can take place when the diamond removes a substantial part of the wheel. However, when one attempts to rub the wheel with the diamond or remove just a small amount of the wheel, the dressing operation does not have a good effect. This means that, if the wheel is returned to the work and, in moving it into that position, it has pass the diamond again, the diamond attempts to remove another layer of material from the wheel. However, because the distance between the axis of the wheel and the diamond remains substantially the same, the diamond attempts to remove an amount of material dictated by the release of pressure in the diamond mount and the release of deflection in the wheel spindle. This means that, on the second pass, the diamond, instead of producing a smooth surface, scores the surface of the wheel or otherwise ruins the perfect surface which had been produced on the first pass. This is particularly true if the speed of advance of the wheel toward the return to the workpiece bore is different from the speed in which it was retracted from the bore past the diamond. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a grinding machine in which the Wheel is subjected to a substantially perfect dressing operation.

Another object of this invention is the provision of a grinding machine in which the Wheel moves past the diamond on a retract and a return strike, but the diamond, during the return stroke, does not ruin the surface previously produced during the retract stroke.

A further object of the present invention is the provi sion of a grinding machine having relatively simple means of assuring that a wheel does not touch the diamond when it is not desirable to do so.

It is another object of the instant invention to provide a grinding machine having a mechanism for producing an improved dress, wherein the mechanism is simple and rugged in construction, is relatively inexpensive to manu- 3,386,210 Patented .inne 4, 1968 Mice facture, and is capable of a long life of useful service with a minimum of maintenance.

With these and other objects in view, as will be apparent to those sliilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

The character of the invention, however, may be best understood by reference to one of its structural forms as illustrated by the accompanying drawings in which:

The single ligure is a somewhat schematic view of the invention, showing particularly the details of the hydraulic circuitry.

Referring to the drawing, the grinding machine, indicated generally by the reference numeral 10, is shown as consisting of a base 11 on which is mounted a compensation table 12. Mounted on this compensation table and slidable transversely is a feed table 13 on which, in the usual manner, is mounted a workhead 2t). Mounted on the base 11 is a dressing apparatus 16, on the end of which is mounted a diamond 17 in the usual manner. The diamond 17 is located so that, as the Wheel 15 leaves the work and returns to it, it must pass by the diamond and be subjected to a dressing operation. Also mounted on the base is a wheelhead 36 having a spindle 14 and an abrasive wheel 15.

Mounted on the feed table 13 is a feed cylinder 1S carrying a piston 19 whose piston rod 21 is fixed in an abutment 22 extending upwardly from the table 12. The grinding machine 1li is, in most respects, similar to the internal grinding machine shown in the patent of Hohler and Hahn, No. 3,197,921, dated Aug. 3, 1965, which shows a grinding machine of the so-called controlled force type.

The grinding machine is provided wit-h a table cylinder 23 which operates to move the wheelhead 30 and the wheel 15 toward and away from the workpiece, a Table' In dash-pot 24, a loading cylinder 25 which serves to load and unload workpieces from the machine, and, of course, the feed cylinder 18 which has been described above. The machine is also provided with a compensation cylinder 26 which joins the compensating table 12 and the base 11 in such a way as to compensate, on occasion, for removal of stock from the abrasive wheel 15 following dress. The machine is also provided with a Wheelhead swivel cylinder 27, a Gage In cylinder 28, and a Gage In cylinder 29. The machine is also provided with diamond turner cylinders 31 and 32 serving to turn and to advance t-he diamond, from time to time. .It should be noted that the hydraulic circuitry is shown in accordance with J.I.C. Standards on Industrial Equipment. Pressure hydraulic fluid is provided by a pump 33 driven by an electric motor 34, From the pump extends a 500 p.s.i. unfiltered line 35. Another output of the pump is connected to a filter 36 from which passes a line 37' and a line 3S, the line 38 being at 50() p.s.i. filtered., While the line 37 operates through a pressure-reducing valve 39 from which extends a line 41 carrying hydraulic fluid at approximately 125 p.s.i. Extending to the circuitry is a drain line 42 which returns all fluid to the sump. The line 35 is joined through a check valve 43 to the table cylinder 23, While the other side of the cylinder is connected by a line 44 to the drain line 42 through a manual shutoff valve 45. The same side of the cylinder 23 which extends to the line 44 is also joined to a line 46 which is connected to a solenoid valve 47, the other side of which is joined by a line 48 to a iiow control valve 49. The other side of which is connected by a line 51 to a Table Index valve 52.

Also `attached to the solenoid valve 52 is a line 53 leading to a Table Out dash-pot 54 whose hydraulic side is connected in a closed circuit through a flow control valve 55. The other side of the dash-pot 54 is joined by a line 56 to the drain line 42. Extending through the hydraulic circuitry is a p.s.i. line 60 which is attached through a check valve 57 to the drain line 42. The Table Index valve 52 is joined by a line 58 to the line 35 and the valve is `also connected by a line 59 to the 5 p.s.i. line 60. The line 46 is joined around the cylinder 23 to the line 35 by a line 61 containing a throttle 62. The same end of the cylinder 23 that is connected to the lines 44 and 46 is also attached by a line 63 to the Table In dash-pot 24. Attached to the end of the dash-pot in the usual way is a check valve 64 and a throttle 65. The 500 p.s.i. filtered line 38 is joined by a line 66 to table hydrostatic control pockets 67 which drain through a line 68 to the drain line 42.

The 500 p.s.i. line 38 is connected by a line 70 to the load valve 69 which, in turn, is joined by a line 71 to one side of the load cylinder 25. The other side of the cylinder is attached through a valve 73 by a line 74 back to the valve 69 whose drain side is connected by a line 75 to the 5 p.s.i. line 60. The 125 p.s.i. line 41 is joined by a line 76 to the cross-slide compensation valve 77, the other side of which is attached by a line 78 to the compensating cylinder 26. The other side of the compensating cylinder is joined by a line 79 to the valve 77 whose drain side is connected by a line 80 to the 5 p.s.i. line 60.

The 500 p.s.i. line 38 is attached by a line 81 to a low-force pressure-regulating valve 82 and also to a highforce pressure-regulating Valve 83. The output side of the valve 82 is connected by a line 84 to the cross-slide valve 85, while the valve 83 is similarly joined to the valve 85 by a line 86. The valve 85 is attached by a line 87 to the cross-slide feed valve 88, the other side of which is connected by a line 89 to the 5 p.s.i. line 60. The line 87 is also joined through a valve 91 to a line 92. The central portion of the line 92 is connected through a valve 93, through a low-force valve 94 to the drain line 42 by a line 95. The 125 p.s.i. line 41 is joined to a backoif high pressure valve 96, the other side of which is connected by a line 97 to a backotf valve 98, the other side of which is connected to a line 101 and the valve 99 is connected by a line to the drain line 42. The line 101 is connected to ya cross-slide damper 102, the other side of which is attached to a line 103. The line 92 is joined to the outer end of the cylinder 18, while the line 103 is connected through the piston rod 21 to the inner end of the cylinder 18 above the head of the piston 19.

The 500 p.s.i. line 38 is attached by a line 104 to a back-off pressure-regulating valve 105 whose output is connected by a line 106 to the drain line 42 through a back-off pressure orifice 107. Between the orifice 107 and the valve 105 is attached a line 108 leading through a check valve 110l to the line 97.

The 500 p.s.i. line 38 is joined by a line 111 directly to a compensation slide pre-load cylinder 112. The 500 p.s.i. line 38 is also connected by a line to a damper by-pass valve 113 whose output is attached by a line 114 to the hydraulic control end of the damper 102. The line 38 is also connected by aline 115 to cross-slide hydrostatic control pockets 116. These pockets are joined by a line 117 to the drain line 42. The line 117 also receives fluid arriving in a line 118 originating in the line 103 and from a line 119 originating in the line 92. The 500 p.s.i. line 38 is connected by a line 121 to the wheelhead swivel valve 122 which, in turn, is attached by a line 123 to the wheelhead swivel cylinder 27. The other side of the wheelhead swivel cylinder is connected by `a line 124 back to the valve 122 whose drain side is joined by a line 125 to the 5 p.s.i. line 60.

The 500 p.s.i. line 38 is attached by a line 126 to a single jet gage valve 127 which, in turn, is joined by a line 128 to the Gage In cylinder 28. The other side of the cylinder 28 is connected by a line 129 back to the valve 127 whose drain is joined by a line 131 to the 5 p.s.i. line 60. The 500 p.s.i. line 38 is joined by a line 132 to a double jet gage valve 133, the other side of which is connected lby a line 134 to the Gage `In cylinder 29. The other side of the cylinder 29 is attached by a line 135 to the drain line 42 and the drain side of the solenoid valve 133 is joined by a line 136 to the drain line 42.

The 500 p.s.i. line 38 is connected 'by a line 137 to a diamond turner valve 138, the other side of which is attached by a line 139 to the diamond turner cylinders 31 Iand 32. The other side of the cylinder 31 is joined by a line 141 back to the valve 138 whose drain is connected by a line 142 to the 5 p.s.i. line 60.

The operation of the apparatus will now be readily understood in View of the above description. The cycle of the machine is controlled by the solenoid valves 52, 47, e9, 77, 85, 88, 94, 98, 113, 122, 127, 133, 138, 96, and 102 which, in turn, are regulated by electrical controls operating on the coils of the solenoids. The electrical control box is of the conventional nature and is well-known in this art. At a certain part of the cycle, it is necessary to withdraw the abrasive wheel 15 from the bore in the workpiece. For that purpose, the table cylinder 23 is actuated and the abrasive wheel 15 is withdrawn from the workpiece and moves axially. Before the wheel passes the diamond, however, the table 13 carrying the abrasive wheel 15 is moved into back-olf position. The 35 pound pressure output of the valve passes through the line 108 and the check valve 110 through the line 97 and the solenoid valve 98. This iiuid pressure operates on the piston 19 and moves the table forwardly (to the left in the drawing) which moves the wheel 15 away from the surface of the work into a back-olf position at which time it moves axially and moves past the diamond 17. The back-of position is located so that the diamond 17 removes a slight amount of the surface of the wheel 15. The wheel moves outwardly to the end of its retracted position and, then, the table cylinder 23 is reversed by means of the Table Index valve 52 and the abrasive wheel 15 moves back along the same path toward the workpiece bore. Then, before the abrasive wheel passes the diamond 17, the valve 96 is opened so that the 125 p.s.i. fluid flows into the line 97. This closes the check valve so that the 125 p.s.i. is felt in the cylinder 18 and presses against the piston 19. This causes all the elements of the machine to stretch slightly and to carry the abrasive wheel 15 slightly away from the diamond 17 so that it does not touch itfas it moves toward the workpiece. Once the abrasive wheel 15 has passed the diamond 17 without contact and enters the bore of the workpiece, the normal feed apparatus is actuated, including the cross-slide valve 85 to regulate the oil in the cylinder 18 and, therefore, the feeding of the abrasive wheel toward the surface of the workpiece.

It can be seen that, when the present apparatus is used in a grinding machine, a clean sing1e-pass dress is obtainable. Then, when the wheel moves back across the diamond, the diamond does not touch the wheel and does not damage or change the clean surface previously obtained by removal of a substantial portion of the Wheel. It can also be seen that the slight movement of the wheel away from the dressing position by metallic deformation 0n the return stroke assures that the wheel is returned to the same position relative to the diamond when it goes into the bore of the workpiece as it did when it previously passed over the diamond. This is important when the finished size of the workpiece is related to the diamond position as is true in many grinding machine cycles.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention yto the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:

l. A grinding machine for iinishing a surface of -revolution of a workpiece comprising (a) a base,

(b) a workhead mounted on the base and adapted to sup-port the workpiece and to rotate it about the axis of the said surface,

(C) a wheelhead mounted on the base and carrying a rotatable abrasive wheel,

(d) dressing apparatus mounted in a location which is fixed relative to the workhead,

(e) means bringing about relative movement between the wh-eelhead and the workhead in a direction along the axis of the said surface to cause the abrasive wheel to engage the dressing apparatus during an outward movement and be dressed thereby,

(f) and means bringing about relative movement by metallic deformation between the wheelhead and the workhead transversely of the said axis when the movement in the direction along the axis takes place during an inward movement to assure that the abrasive wheel does not engage the dressing apparatus.

2. A grinding machine as recited in claim 1, wherein a hydraulic linear actuator brings about feeding movement of the wheelhead relative to the workhead transversely of the axis, the actuator being in locked condition during the said outward and inward movement, but being subjected to additional hydraulic pressure to bring about the metallic deformation on the inward movement.

3. A grinding machine as recited in claim 2, wherein the hydraulic linear actuator acts directly to produce the feeding movement and the pressure of the abrasive Wheel against the workpiece during grinding takes place at a predetermined force.

4. A grinding machine as recited in claim 2, wherein the additional hydraulic pressure produces a strain in the actuator and associated mechanism so that the abrasive Wheel is moved away from the dressing apparatus as it passes it.

5. A grinding machine as recited in claim 2, wherein a hydraulic system is associated with actuator, the system including a single pump connected to two pressure-regulating valves, the valves being set for supplying substantially diiferent output pressures to two lines, a solenoid valve in the low pressure line and a check Valve in the high pressure line, the two lines being connected together downstream of the said solenoid valve and check valve to a line leading to the actua-tor.

References Cited UNITED STATES PATENTS 2,442,683 6/1948 Green 51-50 2,473,670 6/1949 Wilson 125-11 2,680,941 6/1954 Hahn 51-50 X 2,932,130 4/1960 Blood et al 51-50 3,197,921 8/1965 Hohler et al. 51-103 LESTER M. SWINGLE, Primary Examiner. 

